Centrifugal release ball check valves have been utilized in transmission structures to release residual fluid from the apply chamber for a piston-controlled rotating friction device, such as a brake or clutch, when the friction device is disengaged. If no such check valve were present, centrifugal force exerted on the residual fluid may actuate the piston and engage the friction device at an undesirable time. In the structures wherein the friction device and its actuator rotate at relatively high engine speeds and where relatively large diameters are employed, thus developing relatively high centrifugal forces, it is most difficult if not impossible to construct a centrifugal pressure head release valve in which the ball readily seats and properly seals the exhaust port when necessary to maintain fluid pressure in the apply chamber and then readily unseats when required to bleed off the residual fluid. The high centrifugal force on the ball makes it difficult for the fluid pressure to maintain the ball seated. If the valve seating angle is made wide enough to facilitate reliable unseating when desired, the centrifugal force on the ball is likely to unseat it during the presence of fluid pressure. On the other hand, if the seating angle is narrowed sufficiently so that the ball cannot be unseated by centrifugal force when there is fluid pressure, the ball will then sometimes wedge in its seat and fail to eject when fluid pressure is removed.
As a consequence, prior centrifugal pressure head release valves have been subject to a maximum speed limitation so that the centrifugal forces may be kept within a workable range. Such valves could not be used when the fluid actuator had to operate at extremely high rotational speeds. This shortcoming has now been remedied by the present invention. The disclosed centrifugal pressure head release valve functions properly at rotational speeds considerably greater than heretofore possible.
Accordingly, it is an object of the invention to provide a new and improved centrifugal pressure head release valve for a fluid actuator.
It is another object of the invention to provide a novel centrifugal release ball check valve suitable for use at much greater speeds than previously possible.